1.3 Drifting Continents


Vocabulary


    • continental drift: the idea that the continents slowly drifted across Earth's surface
    • fossil: any trace of ancient organism that was preserved in rock
    • pangaea: means"all lands", or that all continents were together

outline


The Theory of Continental Drift


  • the hypothesis that all the continents were once joined together about 300 million years ago it was called pangaea
    • scientists got evidence from land forms,fossils and climate
      • this was called continental drift



Evidence from Landforms



  • scientists found evidence from landforms. They say that the mountain range running from east to west in South Africa
lines up with a mountain range in Argentina. European coal fields match up with similar coal fields in Noth America.


Evidence from fossils



  • Scientists used fossils to prove continental drift.
  • the reptiles Mesosaurus and Lysrosaurus have been found in places now separated by oceans.

Example: Neither reptile could have swum great distances across salt water. If it therefore likely
that those reptiles lived on a single landmass that has since split apart.

Another example is that Glossopteris, a fern like plant that lived 250 million years ago.
They have been found in Africa, South America, Australia, India, and Antarctica.
This convinced some scientists that the serperated landmass had once been united,
because the seedlike structures of glossopteris could not have traveled the great distances that seperate the continents today.
The seeds were too large to have been carried from the wind and also too fragile to have survived trip by ocean waves.



Evidence from Climate


  • scientists used climates as examples for Pangaea too.
    • Example: spits bergen lies in the Arctic Ocean north of Norway.
This island is ice-covered and has harsh polar climate. But fossils of tropical plants are found on Spitsbergen.
When these plants lived about 300 million years ago, the island must have had a warm climate.
  • Spits bergen and South Africa changed because the positions of these places on Earth's surface changed.
As a continent moves toward the poles, its climate becomes older.

bibliography



picture of continental drift got from
www.seafriends.org.nz/ oceano/oceans.htm